Mark Tuohey, pictured right, who is an Irish citizen, is a partner in the Washington DC office of law firm Brown Rudnick.

He is a staunch supporter of President Barack Obama and also counts Mr Biden as a close friend.

He is married to Marty Daley, sister of Bill Daley, Mr Obama's former chief of staff, and Richard Daley, former mayor of Chicago.

A new ambassador is due to be appointed by the White House early in the new year to replace Dan Rooney who stepped down from the post earlier this month.

Mr Tuohey has been touted as a possible successor for over a year. However, his name has now moved to the fore. Former President Bill Clinton has also been linked to the posting.

Mr Tuohey's long-standing interest in Northern Ireland – he is a former adviser to the Independent Policing Commission, sits on the board of the American Ireland Fund and is a former director of Cooperation Ireland – is understood to make him an attractive candidate for the job.

Speaking to IrishCentral.com, a Washington source said Mr Tuohey's name is the only one being mentioned on Capitol Hill.

Mr Tuohey has strong Irish roots with his maternal grandparents hailing from Co Tipperary and his paternal grandfather from Co Galway.